wall shear stress is zero in conical nozzle simulation

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brmaciel posted this 20 August 2019

Hello,

I am still very unexperienced with simulation. I tried to simulate a laminar flow of water in a very small conical nozzle, but I get wall shear stress values equal 0 along the nozzle, and then it suddenly goes up to 3000 Pa at the end (end diameter ~0,2um) - image attached. I suppose the shear stress values should be low at the beginning of the nozzle, but definetely higher than 0. What could be causing that?

 

Thank you very much in advance.

Bruna.

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rwoolhou posted this 20 August 2019

To confirm you're modelling a nozzle with diameter 0.2 microns? 

brmaciel posted this 20 August 2019

sorry, my mistake. 200 microns end diameter = 0.2 mm

abenhadj posted this 20 August 2019

If using Fluent solver please check the value there.

Best regards,

Amine

brmaciel posted this 21 August 2019

Hi Amine,

thanks for your answer. Value checked.

inlet diameter: 4 mm

outlet diameter: 0.2 mm

Would you have any idea why I am getting zero wall shear stress?

 

Thanks and best regards,

Bruna

rwoolhou posted this 21 August 2019

Can you plot the contour (or xy plot in 2d) in Fluent and post that? Also post an image of the near wall mesh. 

brmaciel posted this 21 August 2019

Hi, images are attached.

contour zoom

 

mesh:

abenhadj posted this 21 August 2019

Please XY Plot the wall shear stress value along the wall (You are working 2D contour plot does not make a sense.

Best regards,

Amine

brmaciel posted this 21 August 2019

I plotted it in my first post. Shear stress value along the wall. Here it is again:

 

Best regards,

Bruna

rwoolhou posted this 21 August 2019

Please can you do the xy plot in Fluent. Also plot a contour of velocity. 

brmaciel posted this 21 August 2019

Here they are:

 

 

Thanks and best regards,

Bruna

abenhadj posted this 21 August 2019

Can you restrict the plot to smaller range of position? Is your x axis the axis of symmetry?

Best regards,

Amine

brmaciel posted this 21 August 2019

What range would you like to see?

Yes, the x axis is the symmetry axis.

Best regards,

Bruna

abenhadj posted this 21 August 2019

To 0.04

Best regards,

Amine

brmaciel posted this 22 August 2019

If I go to 0.004 in the diagramms, I can see that the shear stress is very low, but not 0. Thanks for the help!

Best regards,

Bruna

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